Hepatic fatty acid profile and gut microbiome responses of ducks induced by dietary n-6/n-3 polyunsaturated fatty acid ratio

Optimizing the dietary fatty acid profile has been recognized as an effective strategy for improving meat quality traits in poultry. The present study aimed to investigate how different dietary n-6/n-3 polyunsaturated fatty acids (PUFAs) ratios influence hepatic fatty acid composition and gut microbiota in ducks, and to identify key microorganisms involved in gut-liver axis regulation. In this study, Runzhou white-crowned ducks were used as a model to explore the effects of dietary n-3 PUFAs content on liver fatty acid composition and intestinal microbiota, and to screen out key microorganisms that mediate gut-liver axis signaling. A total of 112 28-day old Runzhou white- crowned ducks fed with 2 types of diets (with n-6/n-3 PUFA ratios of 1.97 and 17.37) were randomly divided into 2 treatments with 4 replications (14 ducks per replication) for 28 days. A low n-6/n-3 PUFA ratio significantly increased hepatic n-3 PUFA levels (P < 0.05) while reducing n-6 PUFA synthesis. High-throughput 16S rRNA sequencing showed that n-3 PUFA supplementation altered the microbial composition in both the cecum and colon. It also supported intestinal development by maintaining villus structure and overall gut integrity. At the genus level, Bacteroides were enriched in the cecum (P < 0.05), whereas in the colon, n-3 PUFA increased Campylobacter abundance and reduced Pseudomonas. Using a random forest model, 20 and 50 key microbial taxa were identified in the cecal and colonic communities, respectively. Integration with Spearman correlation analysis revealed strong associations between hepatic n-3 PUFA levels and microbial changes. Notably, Caecibacterium_sporoformans showed a positive correlation with multiple n-3 PUFAs, and its abundance in both the cecum and colon increased significantly (P < 0.05). In summary, a low dietary n-6/n-3 PUFA ratio promoted hepatic n-3 PUFA accumulation, reshaped gut microbial communities, and supported intestinal health, highlighting the gut-liver axis as a key pathway for nutritional regulation in ducks.